You likely have secure boot and a Microsoft package key installed in UEFI. They likely did what they are supposed to do and removed the unsigned software.

You must either sign your own UEFI keys using the options in your bootloader that may or may not be present, or you must use a distro that has the m$ signed secure boot shim key. These are the only ways for both m$ and Linux to coexist. Indeed, with a shim key (Fedora/Ubuntu) you can easily have a windows partition on the same drive without issues.

Secure boot is a scheme to steal hardware ownership. Of course they say it is not because the standard specifies a mechanism to sign your own keys. However the standard specification is only a guideline and most consumer grade implementations do not allow custom key generation and signing.

If you need to do your own keys, search for the US defense department’s guide on the subject. It is by far the most comprehensive explanation of the system and how to set it up correctly. They have a big motivation to prevent corporate data stalking type nonsense and make this kind of documentation accessible publicly.

If your bootloader does not allow custom keys, there is a little known tool called Keytool that allows you to boot directly into UEFI and supposedly change the keys regardless of the implemented utility in the bootloader. I have never tried this myself. The only documentation I have found was from Gentoo, but their documentation assumes a very high level of competence.

Windows went a step further on my machine. I thought it had just screwed up my bootloader, but when I went to restore it my Linux partition was completely gone. Windows Update had deleted the partition.

Malware is right.

deleted by creator

Welcome to the club :-) Microsoft, the true champion in overwriting boot loaders since 198…someth.ing TM ©

Yeah, I didn’t risk dual booting. I have Windows 10 in a VM and a Windows 11 To Go USB drive.